The invention relates to a color television display device comprising a plurality of picture display tubes for displaying a colour television signal, each tube having a control electrode for receiving a video signal, a line deflection coil for deflecting in the horizontal direction an electron beam generated in the tube and a field deflection coil for deflecting the electron beam in the vertical direction.
In such a television display device, for example, a colour television projection device, a plurality of display tubes is used in order to increase particularly the luminance of the colour picture displayed. However, in areas which unsaturated colours are displayed a flicker effect may be produced at high luminance, which effect is caused by the comparatively low frequency, namely 50 Hz in accordance with the European standard, of the vertical deflection. In each second the eye receives only 50 light pulses from the picture and at high luminance this number of pulses is below the frequency for which the eye is sensitive to flicker.
It is obvious that the flicker effect may be eliminated by increasing the field frequency. The repetition frequency of the received field synchronizing signals may, for example, be doubled in a simple way, resulting in a field frequency of 100 Hz. However, this measure requires a line frequency which is higher than that of the received line synchronizing pulses, and video stores for storing the video information. For an acceptable quality of the displayed picture this means that rather complicated and consequently costly circuits must be used.